This invention relates to a control panel for a domestic appliance and more particularly, to a contactless touch switch wherein an electric signal is produced at a location remote from the panel when ambient light from a switch position impinging any one of a plurality of photoelectric detectors is altered relative to the ambient light from a non switch position impinging on a photoelectric detector.
In recent apparatus control systems, the tendency has been to employ touch type switching systems that elminate mechanical parts and substantially lower the need for servicing. In some prior art touch systems such as the one disclosed in U.S. Pat. No. 3,819,906-Gould, Jr., conductor pads are disposed on either side of a display panel. This type of control approach necessitates that some of the components be arranged in intimate contact with the panel and, further are subjected to the environment found in the area of the panel. For example, current carrying electrical components must be electrically insulated from the panel touch area. In a domestic cooking range, these controls would be exposed to relatively high temperatures generated by the surface elements. Many of the electronic components employed at the panel area may be sensitive to high temperature and unless protected from excessive heat, they can be damaged. In other applications, such as clothes washing machines, the panel may be subjected to high humidity conditions which can create hazardous electrical conditions and also shorten the life of some of the components.
In some type prior art touch switch systems, optical fibers are employed to direct light to a photoelectric detector wherein interruption of light passing through the optical fiber causes a signal to be produced. A disclosure using light pipes is shown in U.S. Pat. No. 3,937,952, wherein an input light pipe and an output light pipe are arranged so that the amount of light from the input light pipe entering the output light is variable between a first level when a switch is actuated to a second level when the switch is not actuated.
In other types prior art touch switch, as shown in U.S. Pat. Nos. 3,526,775-Friedrick et al, and 3,885,408, light is transmitted directly to detector. In both of these disclosures, a contactless switch is actuated by interrupting light from impinging on a photosensitive device by a portion of the hand.
It is an object of the present invention to provide an optical touch switching system and method that is operable in the presence of ambient light.
Another object of the present invention is to provide an optical panel having a plurality of touch areas wherein a signal is produced at a remote location by the presence of a human finger at one or more preselected areas on the panel.
Another object of the present invention is to provide a system and method for producing a signal in which all of the operable and electrical components thereof are located internally of the structures into which entry is desired.